拱桥短吊索不同轴偏转和腐蚀耦合对其力学性能的影响

Over the past decade, a lot of sling arch bridge accidents occurred, mostly due to the broken of arch bridge short hanger cable which cause the bridge collapsed. Short hanger cables are the key and vulnerable components of the hanger arch bridges.The existing literature show that the important reason why short hanger cables have short life and damaged so that cannot reach the designed life is the displacement of arch rib and deck in the direction of the bridge, which led to short hanger cables have the bending stress under the influence of vehicle load and temperature load. The static load performance and fatigue life under the influence of bending deflection and corrosion of short hanger cables do not be studied deeply. They are lack of theory and experiment data.The research object of this project are parallel wire chill heading anchor cables and steel strand anchor extrusion cables which are commonly used in arch bridge engineering.Steel wire,Steel strand,parallel wires cable and Steel strand cable ,which are the basic units respectively would be analyzed in theory and be studied by experiments. The fine analytic model will be found in hanger cable and its Internal wire. A method for calculating the bending deflection force will be given. The Influence laws in bending stress and corrosion on the mechanical properties will be researched, when Arch bridge short hanger cables have bending deflection as the anchorages are in different axis. The research results will provide the necessary theoretical support for the design and fatigue life estimation of short hanger cables.

在近十年的吊索拱桥损毁事故中，缘由大多是因拱桥短吊索的断裂而引起桥梁坍塌。文献研究表明，导致短吊索短命,且其使用寿命远小于设计寿命的重要原因是在车辆和温度等作用下，顺桥向引起拱肋与桥面的相对位移，导致短吊索两端不同轴而产生弯曲应力，形成局部应力集中，应力集中与腐蚀的耦合作用加速吊索损坏。目前短吊索的静态和疲劳力学性能受两端不同轴引起的弯曲偏转和腐蚀耦合作用的影响规律，尚未得到研究，缺乏理论和试验数据的支持。本项目针对拱桥常采用的平行钢丝冷铸镦头锚吊索和钢绞线挤压锚固吊索，分别对其基本单元钢丝、钢绞线、平行钢丝索和钢绞线索进行理论力学分析和试验研究，建立吊索及其内部钢丝的应力与弯曲偏转角度的关系模型，探求拱桥短吊索在上下锚具不同轴而产生弯曲偏转的情况下，弯曲角度及弯曲应力与腐蚀耦合对吊索力学性能的影响规律，深究吊索断损因素,以采取改进措施,为拱桥短吊索的设计和疲劳寿命估计提供必要的理论支持。

为了研究轴偏转角现象对拱桥吊索受力机理的影响，针对平行钢丝索和钢绞线索两类拱桥吊索，对吊索的类型和边界条件和中、下承式拱桥的桥面形式进行了研究，提出了导致轴偏转角现象的三要素；研究了不同跨径和不同荷载工况下的拱桥吊索极值；建立了吊索不同轴偏转角下吊索的弯曲应力和极限承载力数学模型；采用数值模拟和试验方法，研究了不同轴偏转角下吊索极限抗拉强度、弹性模量、伸长量和变形等指标的变化规律；建立了吊索精细化有限元模型，研究了吊索应力集中、应变不均匀等现象；研究了不同轴偏转角对腐蚀吊索力学性能的影响；研究了不同轴偏转对不同位置蚀坑应力大小的影响；推导得到不同轴偏转角下的吊索S-N曲线，研究了不同轴偏转角下的吊索疲劳寿命变化规律。